Pulse oximetry is a widely accepted noninvasive procedure for measuring arterial oxygen saturation, which provides early detection of hypoxia. FIG. 1 illustrates a pulse oximetry system 100 having a sensor 110 applied to a patient, a monitor 120, and a patient cable 130 connecting the sensor 110 and the monitor 120. The sensor 110 has emitters and a detector, which are attached to a tissue site, such as a finger as shown. The patient cable 130 transmits an emitter drive signal from the monitor 120 to the sensor 110 and a resulting detector signal from the sensor 110 to the monitor 120. The monitor 120 processes the detector signal to provide a numerical readout of oxygen saturation and pulse rate.
FIGS. 2A-B illustrate a pulse oximetry sensor 110. As shown in FIG. 2A, the sensor 110 has an adhesive wrap 205 that positions emitters 250 (not visible) proximate, for example, a finger nail and a detector 260 (not visible) proximate a finger pad. A sensor plug 200 inserts into a sensor connector 135 (FIG. 1) so that plug contacts 201 are in electrical communications with the monitor 120 (FIG. 1) via the patient cable 130 (FIG. 1).
As shown in FIG. 2B, a pulse oximetry sensor 110 has both red and infrared light emitting diode (LED) emitters 210, 220 and a photodiode detector 230. LED pinouts 250 on the plug contacts 201 (FIG. 2A) connect the LEDs 210, 220 to the monitor 120 (FIG. 1). Detector pinouts 260 on the plug contacts 201 (FIG. 2A) connect the photodiode 230 to the monitor 120 (FIG. 1). The sensor 110 may also have an information element 240, such as a resistor. The information element 240 may have various uses, such as an indicator of sensor type, depending on the manufacturer. A pulse oximetry sensor is described in U.S. Pat. No. 6,256,523 entitled Low Noise Optical Probes; a pulse oximetry monitor is described in U.S. Pat. No. 6,826,419 entitled Signal Processing Apparatus And Method; and an information element is described in U.S. Pat. No. 5,758,644 entitled Manual and Automatic Probe Calibration, all of which are assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein.